The LCN Finder on your SDS200 will work on both DMR and NXDN systems. (That also applies to the SDS100, as well as the 436HP & 536HP.)
However, for the frequencies listed for Location 1 on the license, 462.025 and 463.700, there are several other licensees for each in Tarrant County, including some licensed for DMR. No guarantee, of course, that DMR is in use, but they are licensed. The same frequencies also show licenses in Dallas County, so you may have to sort out who's who to get a better starting point. The Tarrant County Regional Water District license is for conventional, not trunked, usage. But there are a number of examples where a user showing as IG, but actually operating as trunked.
The two frequencies for Location 3, 461.5625 and 462.475, each only have one other licensee in Tarrant Count, and those are not showing as licensed for DMR. But there are also licensees in Dallas & Denton County for both 461.5625 and 462.475.
I would suggest that for whichever of the Tarrant County locations are closest to you, that you enter those frequencies as One Frequency Trunked systems (OFT), with the color code set to 'search'. If you receive something on either, you'd see an indication on the screen that it's Conventional, or one of the trunked types such as Connect or Capacity. Setting it as a OFT would also show you whether talkgroups are used. If you can get enough transmissions, then you might be able to weed TCRWD usage from someone else. If these are being used as Conventional, not trunked, you can leave them in an OFT system to sort out any talkgroups in use.